1. Field of the Invention
The invention relates generally to devices that propel forcibly, into the air, spherical objects such as tennis balls or the like, in selected, adjusted trajectories, for practice or training purposes.
2. Description of the Prior Art
It is well known to provide propulsion devices for tennis balls and like spherical objects. It is also known to employ a pressure build-up, within a chamber to which the tennis balls are fed, in such fashion as to cause the tennis balls to be forcibly propelled from a barrel located at a selected angle of inclination, after being temporarily arrested by a detent within the barrel. In the prior art, thus, it has been well known to cause automatic feeding of the tennis balls to the drum or pressurizing chamber, with the intention of causing the balls to be propelled at prescribed, uniform intervals. Such devices as have heretofore been conceived for this purpose, however, have in general been comparatively expensive, and despite the relative complexity and expensiveness of construction thereof, have been unfortunately characterized, in many instances, by a lack of full efficiency. Thus, in some instances the feeding of the tennis balls has been irregular, in that the timed feeding devices, employed for the purpose of feeding the tennis balls into the pressurizing drum, have not operated in such fashion as to be completely charged or loaded with tennis balls as they approach the ball feeding position.
It has further been a characteristic of the prior art that complex mechanisms have been needed within the drum, as for example, it has been characteristic of tennis ball propulsion devices that air flow is induced into the discharge tube or barrel, through an annular chamber surrounding the barrel, a construction which has been made necessary due to excessive open time for the trap door or similar closure located at the entrance to the pressurizing drum.
Typical of the prior art devices is the propulsion device shown in Nielsen U.S. Pat. No. 3,905,349 issued Sept. 16, 1975.